docs: def _change_soi(self, body):
          """Modify the inner parameters of the Kepler propagator in order to place
          the spacecraft in the right Sphere of Influence
          """
  
          if body == self.central:
              self.bodies = [self.central]
              self.step = self.central_step
              self.active = self.central.name
              self.frame = self.central.name
          else:
              soi = self.SOI[body.name]
              self.bodies = [body]
              self.step = self.alt_step
              self.active = body.name
              self.frame = soi.frame